(4) without the prior written consent of Lessor, install an engine (other than an Engine) on the Airframe or a part (other than a Part) on the Aircraft, provided that such installation does not create, or permit to exist, any Liens on the Aircraft except those of the type permitted under Section 14 hereof and those which apply only to such engine or part which has been installed on the Aircraft; and



 (5) without the prior written consent of Lessor, enter into ACMI "wet leases" or charter agreements whereby Lessee retains full operational control of the Aircraft.



 (ii) Subleases. In the event that Lessee seeks to sublease the Aircraft, in addition to securing Lessor's advance written consent to any Permitted Sublease and the terms and conditions thereof, Lessee shall execute and deliver any and all such documents and agreements, and secure all such approvals and consents from any Person or Governmental Entity, as Lessor and any Lessor Lender shall deem reasonably necessary or desirable in order to preserve and protect its respective rights and interests hereunder and under the other Operative Agreements; and provided further that:



 (1) any Sublessee shall be a duly certificated air carrier holding a current and valid U.S. air operator's certificate; 



 (2) any such Sublessee shall have duly executed and delivered a Permitted Sublease and all documents and agreements contemplated thereby, each in form and substance satisfactory to, and approved in writing by, Lessor, such approval not to be unreasonably withheld; and